Failing Web Platform Tests: urlencoded-parser.any.js due to invalid HTTP method

We're currently failing a lot of the WPT tests for url encoding, not because we're doing anything wrong with regard to url encoding, but because we disallow the made-up HTTP method they're using:

```js
let init = new Request("about:blank", { body: val.input, method: "LADIDA", headers: {"Content-Type": "application/x-www-form-urlencoded;charset=windows-1252"} }).formData()
```

We don't need to take any action now, but I'm just raising this as a data point for allowing arbitrary method names.

cc: @jasnell, @kentonv